As a conventional and typical structure for automotive door trims, rear corner trims and other interior components that are mounted on the interior of a vehicle body panel, there is known the laminated structure comprising a resin core member 1 formed into a desired curved shape, and a surface skin member 2 bonded over the surface of the resin core member 1 as illustrated in FIG. 5.
Due to the recent demand for the resin core members 1 to have complicated three dimensional shapes, they are commonly fabricated by the mold press forming according to which resin material in semi molten state is fed into a metallic mold set or a die set for mold press forming to be shaped into complicated three dimensional shapes. In such a case, to the end of simplifying the overall fabrication process, it has been proposed to press bond the surface skin member 2 onto the resin core member 1 at the same time as mold press forming the resin core member 1.
Now, such a process of mold press forming the surface skin member 2 and press bonding the resin core member 1 thereonto is briefly described in the following with reference to FIG. 6 and 7. First of all, a predetermined amount of a resin material in semi molten state is fed onto a lower mold 3 for mold press forming from a gate 3a as illustrated in FIG. 6. A surface skin member 2 is positioned above the lower mold 3 by a clamping device 5 retaining the peripheral part of the surface skin member 2, and an upper mold 6 for mold press forming is placed thereabove in a vertically moveable manner by means of a lifting device not shown in the drawings.
In this case, the surface skin member 2 comprises a resin sheet 2a such as a PVC sheet and a high expansion ratio foamed backing layer 2b consisting of polyolefin resin foam so as to give a soft feel to this surface skin member 2. The expansion ratio of foam material is given as the ratio of the actual density of the resin to the apparent density of the foamed resin.
Thereafter, by engaging and closing the upper and lower molds 3 and 6 for mold press forming with each other, the semi molten resin material 4 is formed into the resin core member 1 and, at the same time, the resin core member 1 and the surface skin member 2 are integrally joined with each other.
However, due to the melting heat (200.degree. C.) for the resin material 4 and the mold press pressure (50 to 80 kg/cm.sup.2) existing during the process of mold press forming illustrated in FIG. 7, collapsing of the foam layer 2b tends to occur, and the resulting surface irregularities of the surface skin member 2 produces an unattractive appearance as illustrated in FIG. 8.
Also, the collapsing of the foam layer 2b causes a fluctuation in the thickness of the foam layer 2b, and the surface texture becomes unattractive due the loss of the soft feel at such thinned portions.
To correct this situation, it is conceivable to use a low expansion ratio material, a foaming material having mutually separated cells, or a high density foaming material for the foam layer 2b, to increase the thickness of the foam layer 2b, or to use a more heat resistant resin. However, in either case, because the material cost is increased, and/or the weight is increased in spite of a general desire to reduce weight, such counter measures have not been acceptable.
Thus, in order to bond a surface skin member 2 having a soft feel over a resin core member I having a desired rigidity, it is necessary to bond the surface skin member 2 onto the resin core member 1 by vacuum forming or the like following the mold press forming of the resin core member 1 as a separate process, and this not only requires large scale production facilities but also causes a substantial cost increase.